The centre or backrower played for the Scorpions in 2012, but after a brief spell in league went to play in the other code, first for Neath, then Bridgend Ravens, before moving to Athletic.
Morgan said: “I’m happy to be back at the Scorpions and still playing rugby league in Wales.
“I had a great first session back last night and it looks like the boys are all working really hard.
“I’m looking forward to the rest of the season and starting off by getting a win on Sunday against Hemel before taking on Crusaders at the Arms Park on May 10.”
Scorpions coach Mike Grady said: “I’m made up that Tom has agreed to return to the club. I’ve been in regular contact with him and he can’t wait to be playing Rugby League again. This is a fantastic boost to us after a slow start to the season.”